Since 1998 Honda has been quietly producing one of the cleanest vehicles in America. In 2001 the EPA called its engine “the cleanest burning internal combustion engine in the world.” No, it’s not a hybrid, it’s Honda’s Civic Natural Gas (formerly known as the Civic GX). Until now, the Civic Natural Gas has only been available for retail sale in a handful of states like California and New York. For 2012, Honda expanded sales to 37 states and lent us one for a week.